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High-light stress and the one-helix LHC-like proteins of the cryptophyte Guillardia theta
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Botany Department, University of British Columbia, Vancouver, BC, Canada)
Botany Department, University of British Columbia, Vancouver, BC, Canada.
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Christiane Funk)
Botany Department, University of British Columbia, Vancouver, BC, Canada.
2011 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 7, 841-846 p.Article in journal (Refereed) Published
Abstract [en]

Cryptophytes like the cryptomonad Guillardia theta are part of the marine phytoplankton and therefore major players in global carbon and biogeochemical cycles. Despite the importance for the cell in being able to cope with large changes in illumination on a daily basis, very little is known about photoprotection mechanisms in cryptophytes. Here we show that G. theta is able to perform non-photochemical quenching, although none of the usual xanthophyll cycle pigments (e.g. zeaxanthin, diadinoxanthin, diatoxanthin) are present at detectable levels. Instead, acclimation to high light intensity seems to involve an increase of alloxanthin. G. theta has genes for two one-helix "light-harvesting-like" proteins, related to some cyanobacterial genes which are induced in response to high light stress. Both the plastid-encoded gene (hlipP) and the nucleomorph-encoded gene (HlipNm) are expressed, but transcript levels decrease rather than increase during high light exposure, suggesting they are not involved in a high light stress response. The HlipNm protein was detected with a specific antibody; expression was constant, independent of the light exposure.

Place, publisher, year, edition, pages
2011. Vol. 1807, no 7, 841-846 p.
Keyword [en]
Guillardia theta, Cryptomonad, High light inducible protein, Non-photochemical quenching, Light-harvesting-like protein
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-42187DOI: 10.1016/j.bbabio.2011.03.011PubMedID: 21459077OAI: diva2:408861
Available from: 2011-04-06 Created: 2011-04-06 Last updated: 2012-09-27Bibliographically approved
In thesis
1. Functional studies on the Light-harvesting-Like (LiL) Proteins in Cyanobacteria and Cryptophytes
Open this publication in new window or tab >>Functional studies on the Light-harvesting-Like (LiL) Proteins in Cyanobacteria and Cryptophytes
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The light-harvesting like (LiL) proteins are a widely spread group of proteins within photosynthetic organisms. They are membrane proteins composed of one to four transmembrane helices and – in homology to the light-harvesting complexes of algae and higher plants – at least one of these transmembrane helices contains the chlorophyll a/b-binding (CAB) domain. Opposite to the light-harvesting antenna complexes, LiL proteins are stress induced and they have been shown to be involved in protection of the photosynthetic apparatus. The work presented in this thesis is focused on understanding the function of one-helical LiL proteins of the cryptophyte algae Guillardia theta and the cyanobacterium Synechocystis sp. PCC 6803. G. theta contains two genes encoding LiL proteins, one is localized in the plastid (hlipP), the other in the nucleomorph (HlipNm). Both genes are expressed in normal growth condition, but they are not induced by high light. Immunostaining indicated that HlipNm is translated, but not light-induced. These proteins therefore seem not to be involved in photoprotective mechanisms of G. theta. In the cyanobacterium Synechocystis sp. PCC 6803 four one-helical LiL proteins were identified, they are called Small CAB-like Proteins (SCPs); a fifth LiL (ScpA) is fused with the ferrochelatase (FC), an enzyme involved in the heme synthesis. Our analysis revealed that SCPs are involved in the de novo assembly/repair cycle of Photosystem II, stabilizing the chlorophyll pigments at their protein scaffold. The in vitro characterization of the recombinant FC showed that ScpA is involved in the product-release of the catalytic domain of the enzyme, thereby regulating substrate availability for chlorophyll- or heme- biosynthesis. Finally, using a transcriptomic and metabolomic approaches, I was able to show that deletion of all SCP genes has profound impact on the cell organization and metabolism. In SCP-depleted cells, production of reactive oxygen species (ROS) is increased, while the amount of Photosystem II per cell volume is decreased, causing a macronutrient-deficient phenotype. Therefore, SCPs are important for stress protection and help to maintain a metabolic equilibrium within the cell.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2012. 67 p.
Photosynthesis, cyanobacteria, Guillardia theta, photosystem II, chlorophyll-binding proteins, onehelix LiL proteins, photoprotection
National Category
Natural Sciences
Research subject
urn:nbn:se:umu:diva-59801 (URN)978-91-7459-486-7 (ISBN)
Public defence
2012-10-26, KBC-huset, KB3A9, Umeå University, Umeå, 10:00 (English)
Available from: 2012-10-05 Created: 2012-09-26 Last updated: 2012-09-26Bibliographically approved

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